Selective Utilization of Polyguluronate by the Human Gut Bacteroides Species

Human gut Bacteroides species play crucial roles in the metabolism of dietary polysaccharides. Polyguluronate (PG), a major component of alginate, has been widely used in the food and medical industries. However, how PG is utilized by human gut Bacteroides species has not been fully elucidated. Here, using a combination of culturomics, genomics, and state-of-the-art analytical techniques, we elucidated in detail the utilization profiles of PG by 17 different human gut Bacteroides species. Our results indicated that each Bacteroides species exhibited a unique capability for PG utilization. Among all species tested, Bacteroides xylanisolvens consumed the highest amount of PG and produced the greatest quantity of short-chain fatty acids, suggesting that it may be a keystone bacterium in PG utilization. Mass spectrometry showed that PG was degraded by B. xylanisolvens into a series of oligosaccharides. Genomic analyses confirmed that B. xylanisolvens possesses a large and divergent repertoire of carbohydrate-active enzymes. Moreover, genomic annotation identified two enzymes, PL17_2 and PL6_1, in B. xylanisolvens that are potentially responsible for PG degradation. Altogether, our study provides novel insights into PG utilization by human gut Bacteroides species, which has important implications for the development of carbohydrate-based drugs from marine resources.